1. Field of the Invention
The present invention relates to medical devices. More particularly, the invention relates to occluding devices for occlusion of fluid flow through a body vessel and a method for making the occluding devices.
2. Background of the Invention
Embolization coils have been used as a primary occluding device for treatment of various arteriovenous malformations (AVM) and varicoceles, as well as for many other arteriovenous abnormalities in the body. Occluding devices are also used to repair abnormal shunts between arteries and veins, prevent or reduce blood flow to tumors, stop hemorrhaging as a result of trauma, and stabilize aneurysms to prevent rupture. Embolization coils may be configured in a variety of sizes with varying diameters and may be made of several different materials including stainless steel and platinum. Moreover, many embolization coils are designed with high tension or stiffness, e.g., between about 60 to 100 weight grams, which may provide the coil with a shape memory. This tension is sometimes referred to as a pre-curled tension. Such coils tend to reform or recanalize back to a coiled or curled shape including, such as for example, a helical and/or looping configuration because of the high tension. Reforming of the coil in the body vessel may be desirable to enhance occlusion of fluid flow therethrough.
Some of these embolization coils may also be coated for various reasons including inducing more robust and stable occlusions and/or improving long term recanalization rates. For example, embolization coils may be coated with a bioresorbable coating, a biocompatible material or another suitable material depending on the desired function.
Current manufacturing processes for coating embolization coils typically involve coating the embolization coil which has a pre-curled tension. The coil is either coated in a curled configuration or allowed to curl after being coating but prior to being deployed. The coated coil is then substantially straightened so as to be advanced through a catheter or other delivery device for introduction into the body vessel. However, some coatings, due to their limited mechanical properties (e.g. stress-strain characteristics), are susceptible to cracking and/or chipping when the coated coil is straightened from its curled shaped. Cracking and/or chipping of the coating, especially prior to introduction of the embolization coil into the body vessel, may result in a loss of the coating and a corresponding loss in occluding performance.
In view of the above, it is apparent that there exists a need for an improved occluding device and a method for making such an occluding device.